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Recent research themes

Resonant x-ray scattering

Resonant x-ray scattering is emerging as a powerful new tool to study electronic ordering in materials like the high temperature superconductors or the colossal magneto resistance manganite materials. In conjunction with groups at the University of British Columbia, we have developed a new state-of-the-art facility for this technique at the Canadian Light Source, the new 3rd generation synchrotron in Saskatoon. The power of this technique is to combine x-ray scattering, which probes spatial order, with x-ray spectroscopy, which probes electronic structure and is sensitive to different atomic species, as well as different valence, magnetic and orbital states within an atomic species. This combination allows one to probe very directly and considerable detail a variety of exotic magnetic (spin), charge, orbital or structural order phenomena.

Contact: David Hawthorn

Super solid phases

Supersolids are unique quantum phases that display simultaneous “crystal” and “super” order. Like normal crystals, they have a regular lattice structure and well defined density order. However, unlike familiar classical crystals, these phases harbor unconventional quantum behavior more characteristic of superfluids or superconductors. Recent experimental work has suggested the observation of super-flow characteristics in solid (crystalline) Helium-4, sparking a worldwide interest in this possible rare example of a new elemental phase of matter. Here at Waterloo, researchers are interested in many of the fundamental properties of supersolids, in both continuum and lattice systems.

Contact: A. Burkov and R. Melko

Low temperature physics

Our department has advanced facilities to study the low-temperature physics of a variety of magnetic materials, micron and sub-micron scaled devices (such as sSETs and SQUIDS), and exotic superconducting systems. Physical measurements that we are currently interested in include: specific heat and susceptibility of unconventional magnetic materials; 1/f noise in Josephson Junction arrays; dissipation in sSETs; thermal conductivity in exotic superconductos; and more.

Contact: R. Hill and J. Kycia

Frustrated magnets

Frustration arises when a magnetic system cannot minimize its total classical ground state energy by minimizing the energy of each pair of spin-spin interaction individually. For example, this arises for antiferromagnetically coupled spins on triangular and face-centered cubic lattices. The phenomenon of frustration is an ubiquitous one in condensed matter physics. It arises in magnetic systems, molecular crystals, superconducting Josephson junction arrays. There is an enormous amount of current research devoted to the study of strongly frustrated antiferromagnets since it has been suggested that these could exhibit novel non-Neel ground states with zero staggered sublattice magnetization. However, intriguing experimental results find that a large portion of the materials studied show a magnetic spin-freezing transition similar to what is found in higly disordered magnetic materials, The origin of this spin-freezing constitutes a major puzzle in this field: is the freezing intrinsic to the idealized pure material, or is it driven by the weak amount of random impurities at the 1% level? Also, what is the combined effect of random disorder and quantum fluctuations in these systems? Which one of random disorder or quantum fluctuations "wins"?